Method and apparatus for media distribution using VPLS in a ring topology

ABSTRACT

A method or corresponding apparatus is employed for distributing media on a ring network. Multiple nodes and communications links are configured to distribute media in the ring network. Distribution of the media is disabled on a communications link between a selected pair of adjacent nodes in the ring network in a manner maintaining communications between the selected pair of adjacent nodes other than for distribution of the media. This configuration results in a “horseshoe” topology of the ring network with respect to the media, where distribution of the media on the ring network occurs in one or two downstream directions from head-end ingress node(s) on the ring network. Virtual Private LAN Service (VPLS) may be employed to transport the media. In an event of a link or node failure, the disabled link is enabled, allowing for continued distribution of the media with network recovery in a timeframe typically unobservable by an end user.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/783,619, filed on Mar. 17, 2006. The entire teachings of the aboveapplication are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Two useful attributes for media service delivery, such as video servicedelivery, are network quality and high-availability. On today's HybridFiber Coaxial (HFC) networks, this is achieved because the technologydeployed is mature and the network is largely dedicated to just a singlefunction—media service delivery. However, when moving the media servicesinto a Packet Switched Network (PSN) arena, achieving high levels ofservice quality and availability becomes a challenging task.

Today's HFC video networks are, in general, very scaleable. Severalmillion customers are serviced from large-scale head-end installations,which then feed distribution networks for user access. To compete withHFC networks, an Internet Protocol (IP) video network must be capable ofscaling to a similar capacity. In a typical network architecture,devices must be able to scale from a few hundred users in the earlystages of implementation to multiple-millions of users at the peak ofthe service deployment. Additionally, in typical situations, it becomesnecessary to add other services, such as voice and high-speed data, whena decision is made to provide a “triple-play” offering. All this must beaccomplished without compromising the reliability, quality,manageability, or serviceability of the network.

SUMMARY OF THE INVENTION

An embodiment of the present invention includes a method orcorresponding apparatus of distributing media on a ring topologycommunications network. Multiple nodes and communications links areconfigured to distribute media in a ring network. Distribution of themedia on a communications link between a selected pair of adjacent nodesin the ring network is disabled in a manner maintaining communicationsbetween the selected pair of adjacent nodes other than for distributionof the media.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particulardescription of example embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe example embodiments of the invention.

FIGS. 1A-1C are network diagrams illustrating an embodiment of thepresent invention;

FIGS. 2A-2F are network diagrams illustrating a technique of configuringa network with an embodiment of the present invention;

FIGS. 3A-3D are network diagrams illustrating another embodiment of thepresent invention; and

FIGS. 4A-4C are flow diagrams illustrating embodiments of the presentinvention.

FIGS. 5A-5B are network diagrams illustrating an example embodiment ofthe present invention;

FIG. 6 is a flow diagram of an example embodiment of the presentinvention;

FIG. 7 is a block diagram illustrating example components that may beused in an example embodiment of the present invention; and

FIG. 8 is a table illustrating a hierarchy of backup communicationspaths optionally used in an example embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A description of example embodiments of the invention follows.

An embodiment of the present inventions includes a method orcorresponding apparatus for distributing media in a ring topologynetwork, optionally using Virtual Private Local Area Network (LAN)Service (VPLS). In this embodiment, the network may be designed suchthat there is a logical break in the ring, optionally in the center ofthe ring. The logical break (a) may be between (i) head-end ingress nodeon the ring network receiving media from a head-end node external fromthe ring network and (ii) an adjacent node in the ring network or (b)may be between two adjacent nodes downstream of the head-end ingressnode. In the former embodiment, the head-end ingress node sends themedia in one downstream direction. In the latter embodiment, the ingresshead-end node sends data downstream in two directions on the ringnetwork in a normal scenario. In a failure scenario, data may passcertain segments of the ring twice.

An embodiment of the present invention may leverage VPLS andMulti-Protocol LAN Service (MPLS) technologies. In utilizing VPLS, theembodiment may create a “replicate and forward” methodology formulticast traffic replication. This may be accomplished because the VPLSdomain may appear as a large layer 2 switch when viewed from aprospective of any of the VPLS domain pseudowire (PSW) circuits. MPLSmay be used as the underlying transport for the VPLS PSWs and mayprovide part of carrier-class redundancy.

FIG. 1A is a network diagram of a network 100 illustrating aspects of anembodiment of the present invention. A part of the network 100 isconfigured as a ring network 105 with six nodes 110, which may beaggregation nodes, connected via physical communications links 115. MPLSLabel Switched Paths (LSPs) 120 may be configured in a manner traversingthe communications links 115 and carrying pseudowires 125.Communications traffic, media traffic, or other forms of traffic, suchas narrowband communications or data, ride on the MPLS LSPs 120 orpseudowires 125, as known in the art.

In the network 100 of FIG. 1A, a service provider may configure themultiple nodes 110 and communications links 115 to distribute media inthe ring network 105. According to an embodiment of the presentinvention, the service provider may also disable distribution of themedia on a communications link, such as a communications link 135between a selected pair of adjacent nodes 130 a and 130 b in the ringnetwork 105 in a manner maintaining communications between the selectedpair of adjacent nodes 130 a, 130 b other than for distribution of themedia.

The network 100 may also include a head-end (HE) node 155 that providesmedia (e.g., video content) 165 to the ring network 105 at node S1(i.e., head-end ingress node) of the multiple nodes 110. The media 165may be switched throughout the ring network nodes S2 through S6 at layer2 via VPLS. At each node 110, a “replicate and forward” function may beemployed for true multicast transmission by forwarding the traffic intwo directions: (1) downstream for distribution to a Digital SubscriberLine Access Multiplexer (DSLAM) system 140, FTTx termination devices145, Layer 2 switches, IP routers, Reconfigurable Optical Add/DropMultiplexers (ROADMs), Cable Modem Head-ends, etc., and (2) downstreamto the next node on the ring network 105.

The head-end node 155 may receive media from upstream sources, such as asatellite farm 160 a or a middleware server farm 160 b. Video or othermedia content can be distributed using any of multiple forms ofdistribution technologies, such as spanning tree, Resilient Packet Ring(RPR), token passing, Bi-directional Line Switched Ring (BLSR),Uni-directional Path Switch Ring (UPSR), layer 3 technologies, such as amulticast routing protocol (e.g., protocol independent multi-cast,sparse node (PIM-SM), which may or may or not be MPLS enabled), layer 2technologies, such as VPLS, transparent bridging (without VPLS),Internet Group Management Protocol (IGMP) snooping, point-to-multi pointprotocol, or a layer 1.5 drop and continue mode protocol.

Continuing to refer to FIG. 1A, the ring network 105 has acommunications link 115 that is configured as a logical break 135 withrespect to distribution of the media 165. Thus, the ring network 105 canbe considered a “horseshoe” topology, though the topology describedbelow in reference to FIGS. 3A-3D more clearly illustrates the“horseshoe” topology. The logical break 135, across which distributionof the media is disabled, prevents a loop in the ring network 105. Ifthere is a fault, a typical work-around is employed that is notdependent on the horseshoe topology. In some embodiments, thework-around includes enabling distribution of the media 165 via thecommunications link 175 previously configured with the logical break135.

In the embodiment of FIG. 1A, the two nodes 130 a and 130 b on each sideof the disabled link 135 are aware of the disabled link 135; other nodesmay or may not be aware of the disabled link 135. Thus, the horseshoetopology may be preconfigured in a manual manner or via a NetworkManagement System (NMS).

Benefits of the horseshoe topology for service providers include nothaving to add information to communications nor having to run a controlprotocol to break the loop (e.g., spanning tree (layer 2) or PIM (layer3)). In one embodiment, MPLS may be employed in the ring network 105.VPLS and MPLS may be used for a layer 2 loading, forwarding, orreplication of packets. VPLS allows media service (e.g., video streams)at guaranteed Quality of Service (QoS) dedicated bandwidth (BW) and maybe used to interact with IGMP snooping.

Because VPLS is commonly used to deliver a Virtual Local Area Network(VLAN) type of service, it usually employs a full mesh of MPLS LSPs andVPLS PSWs between the sites of a particular VPLS domain. Thisconfiguration is derived from a need for all sites to know how to reachall of the other sites within their VPLS domain. However, the nature ofIP multicast traffic is somewhat different. IP multicast does notrequire that each of the VPLS domain members knows how to reach allother members in the domain—it only knows how to reach its neighboringnode. This change relaxes the need for full mesh topology, which leadsto a decrease in the required number of LSPs/PSWs employed in thenetwork, thereby simplifying network topology, implementation, andsupport. Then, the multicast traffic may be “replicated and forwarded”on a per node basis, and this may be responsible for ensuring that allrelevant multicast traffic reaches all of the specified downstreamnodes.

FIG. 1B illustrates how the network 100 can be self-healing andresilient. The same IP media content distribution network as FIG. 1A ispresented in FIG. 1B; however, this network 100 has a link cut 170between nodes S1 and S2. In an event a link cut 170 occurs, illustratedas a severed communications link between nodes S1 and S2, a PSW 171,which rides on a backup LSP 172, is employed to get the media trafficfrom node S1 to node S2.

When nodes S1 and S2 detect the link failure 170, they switch over tothe pre-provisioned or signaled backup LSP 172, and an associated PSW171 follows this LSP 172. Traffic then flows from node S1 in acounter-clockwise direction to node S2 via the other nodes (S5, S4, andS3) along the way, and service is restored within a short amount oftime, such as 7 msec. MPLS Fast Re-Route (FRR) technology may beemployed to ensure restoration of distribution of the media within aspecified length of time.

FIG. 1C illustrates a scenario in which there is a complete node failure175. To address this worst case scenario, a second primary LSP 177 maybe provisioned on each node in the ring network 105. This second primaryLSP 177 is not a backup LSP, but actually a second primary LSP thatprovides a redundant connection in an event of a complete node failure175. A secondary PSW 176 rides on the second primary LSP 177 betweennodes S2 and S4. Because of a requirement for backup LSPs to have thesame end nodes as their primary counterparts, this new LSP 177 is aprimary, not a secondary, LSP. However, the new primary LSP 177 may havea lower weight when compared to the preferred primary LSP so that it isused in an event of a preferred primary and backup LSP completefailure—a condition that exists if a node fails, such as node S3.

It should be understood that, following the node failure 175 of node S3,the communications link 115 with the logical break 135 between theselected pair of adjacent nodes 130 a, 130 b is enabled to carry themedia via the PSW 176 that rides across the lower weighted primary LSP177 between nodes S2 and S4. Enabling the initially disabledcommunications link (i.e., communications link 115 with the logicalbreak 135) may occur both in an event of a node failure 175 or, asillustrated in FIG. 1B, a link failure 170.

FIGS. 2A-2F illustrate another embodiment of the present invention inwhich a configuration embodiment of a ring network is illustrated.Referring first to FIG. 2A, a network 200 with a ring network 205employs network nodes 210, including nodes A, B, C, and D. Between thenetwork nodes are physical links 215. On three of the four physicallinks 215 are LSPs 220 a-b, 220 b-c, and 220 c-d. On the fourth of thefour physical links 215, between nodes A and D, is a physical link 215with a logical break 235 with respect to carrying media between nodes Aand D, which are a selected pair of adjacent nodes 230 a, 230 b. Media265 (e.g., video content) may be received from a middleware server farm260 a or a video head-end node 260 b, or other media source (not shown).As illustrated, the media 265 may be dropped from node C to a DSLAM 240,and further distributed to end user terminal devices 245 (not shown).

In the embodiment of FIG. 2A, it is assumed that node A is in a CentralOffice (CO) and has no subscribers receiving the media 265 from it.Nodes B, C and D may have IP DSLAM(s) connected to them. It should beunderstood that the physical ring of the ring network 205 is closed, butthe LSP ring is not closed, i.e., there is no LSP from node D to node Ain this example network configuration and no media traffic flows overthis link, except in cases of failure(s) in the network.

FIG. 2B illustrates a first configuration step in which an LSP 220 a-bis configured from nodes A to B, optionally with a Fast ReRoute (FRR)facility. Primary LSPs are configured on a per hop basis. In this case,an LSP is created to carry communications between node A and node B. Thesame steps are created for nodes B to C and nodes C to D. In oneembodiment, on configuring each primary LSP, a MPLS fast reroute (FRR)facility is employed. This automatically creates a backup LSP 272 a--bin the opposite direction of the LSP 220 a-b it is backing-up. In theexample of FIG. 2B, this backup LSP 272 a-b is automatically provisionedfrom node A to node D to node C on its way to node B. Note that thebackup LSP 272 a-b is not terminated in a hop-per-hop manner atintermediate nodes A, D, and C, but is transparently passed throughthem. The backup LSP 272 a-b is terminated at node B, which is itsprotect node, as understood in the art. It is also understood in the artthat there is no traffic flow over the backup LSP 272 a-b when it isacting in a standby mode.

FIG. 2C is a diagram illustrating a backup facility LSP 217 betweennodes A and B. MPLS may be employed to facilitate FRR backup LSPs 272b-c and 272 c-d, which are backing-up a primary LSP 220 a-b on a linksegment between two nodes (e.g., node A and node B). The backup LSPs 272b-c and 272 c-d may share the same facility backup LSP 217 or usedifferent facility back-up LSPs. Sharing one facility backup LSP 217 mayconsume less control bandwidth since one large facility LSP can becreated.

FIG. 2D is a network diagram at a next point in configuring anembodiment of the present invention. A backup LSP 220 b-c is createdfrom node B to node C, optionally with a Fast Re-Route (FRR) facility.In one embodiment, a backup LSP 272 a-b is configured when the primaryLSP 220 a-b is configured between nodes A and B.

FIG. 2E is a network diagram illustrating LSPs 220 a-b, 220 b-c, and 220c-d configured on the four node network across physical links (notshown) other than the communications link with the logical break 235disabled from distributing media absent a node or link failure in thering network 205. The backup LSPs 272 a-b, 272 b-c, and 272 c-d areoptionally configured on the ring network 205. Having the backup LSPsconfigured allows for rapid recovery from a failure on a differentcommunications link failure or a network node failure.

FIG. 2F illustrates a scenario in which there is a communications linkfailure 270. The backup LSP 272 b-c for node C flows from node B to A,then from node D to node C, recovering media distribution in less than50 msec (in some embodiments) following the communications link failure270. Nodes B and C have drop and loopback configurations 273 a, 273 b,respectively, to distribute the media 265 to its destination(s). Forexample, node C may replicate video traffic onto a primary LSP 220 c-dfrom node C to node D for transporting the video traffic from node C tonode D.

In reference to FIGS. 1A-1C and 2A-2F, it is described above how anetwork can provide an extremely resilient architectural solution fordelivery of IP media services, such as video. However, the previoustopologies suffer from one weakness—a single point of failure at thehead-end ingress node S1. This weakness can be addressed by using adifferent embodiment of the “horseshoe” topology.

As described above in reference to FIGS. 1A-1C and 2A-2F, a logicalbreak (i.e., logical breaks 135 and 235, respectively) in traffic flowmay be installed between the last ring node and the ingress (i.e.,head-end) ring node because, if this break does not exist, multicasttraffic flows backupon itself throughout the ring network. In thetopology examples of FIGS. 1A-1C and 2A-2F, this logical break 135, 235,respectively, is installed between the ingress node S1 and the last nodein the ring S6; however, if the logical break is moved to be more towardthe center of the ring, it becomes possible to avoid having a singlepoint of failure at the head-end ingress node.

FIG. 3A is a network diagram of a network 300 that illustrates anotherembodiment of the “horseshoe” topology. In the example network 300,there are two logical breaks 335 a, 335 b in the ring network 305instead of just one—one logical break 335 a between a selected pair ofadjacent nodes 330 a and another logical break 335 b between thehead-end ingress nodes 330 c and 330 d, respectively. Again, theselogical breaks 335 a, 335 b are used to constrain traffic to aparticular side of the ring network 305 during normal operations.

The network 300 includes similar network nodes and communications linksas presented in reference to FIG. 1A. For example, a satellite farm 360a and middleware server farm 360 b provide media 365 to the head-endnode 355. In the normal operational state, traffic flows from thehead-end node 355 into both of the head-end ingress nodes S1 a and S1 b330 c, 330 d, respectively. Each ingress node then forwards traffic onto its particular half of the ring; that is, node S1 a feeds nodes S2and S3 and node S1 bfeeds nodes S4 and S5. The physical links 315 withlogical breaks 335 a, 335 b between nodes S3/S5 and S1 a/S1 b,respectively, may be used for distributing the media 365 only duringnetwork faults in one embodiment. Similar physical links 315, MPLS LSPs320, and pseudowires 325 are employed in the network 300 of FIG. 3A aswere employed in the network of FIG. 1A, and the MPLS LSPs 320 andpseudowires 325 are used in a corresponding manner.

FIG. 3B is a network diagram in which the network 300 has a link cut (orfailure) 370. Recovery after a link failure with this “horseshoe”topology is similar to what was presented in reference to FIG. 1B.Specifically, in one embodiment, upon detection of the link cut 370, thenodes S1 a and S2 neighboring the link cut 370 begin forwarding trafficacross a backup LSP 372 and accompanying pseudowire (PSW) 371. Within 7msec, for example, node S1 a begins forwarding traffic across the backupLSP 372 to node S2. When in the recovery configuration, the trafficflows in an opposite direction as normal traffic flow absent the linkcut 375 a. Node S2 then continues traffic flow to node S3.

FIG. 3C is a network diagram of the network 300 in which a node failure375 a occurs. Recovery after a complete node failure with thisembodiment of the “horseshoe” topology is similar to what was presentedearlier in reference to FIG. 1C. Upon detection of link failuresresulting from the failed node, the neighboring nodes begin forwardingtraffic across a new preferred connection of a secondary PSW. The newPSW is riding on top of a new primary LSP, as understood in the art. Forexample, in the network diagram of FIG. 3C, node S2 has completelyfailed 375 a. This has resulted in failure of all LSPs and PSWsinvolving node S2. When nodes S1 a and S3 detect the failure, apre-provisioned secondary PSW 371 between nodes S1 a and S3 becomes thepreferred traffic path, and service is restored. After the node failure375 a is corrected, the network configuration may be returned to the“horseshoe” topology with disabled communications links 315 havingrespective logical breaks 335 a, 335 b.

FIG. 3D is a network diagram of the network 300 in which one of thehead-end ingress nodes, node S1 a, receiving communications from ahead-end node 355 experiences a complete failure 375 b. Recovery after acomplete head-end node failure 375 b is very similar, in someembodiments, as to what occurs in the node failure of FIG. 3C. Thedifference is that, during recovery, the remaining operational ingressnode, node S1 b, serves the entire ring topology, not just half as innormal operation. In the network diagram of FIG. 3D, node S1 a hascompletely failed 375 b. This has resulted in the failure of all LSPsand PSWs involving node S1 a. In addition, all customers served by thetop half of the ring (i.e., nodes S2 and S3) are in jeopardy ofexperiencing a loss of communications containing media 365 or othercontent. When nodes S1 band S3 detect the failure of node S1 a, apre-provisioned secondary PSW 371 between nodes S1 b and S2 becomes apreferred traffic path for the remaining active nodes on the top half ofthe ring (i.e., nodes S2 and S3) to receive communications with themedia 365 or other content. In the recovery state, traffic flows fromthe head-end node 355 into node S1 b, across the secondary PSW 371 tonode S2 via a communications link 315 (previously configured with alogical break 335 a) between network nodes S5 and S3, and thendownstream on the top half of the ring (i.e., from node S3 to node S2).Traffic on the PSW 371 is only forwarded by the intermediate nodes (S4,S5, S3) and not sent to locally attached DSLAMs on these intermediatenodes. Once node S2 receives the media traffic over the secondary PSW371, it then continues sending the traffic downstream to node S3. Notethat traffic flowing on the bottom half of the ring (i.e., nodes S1 b,S4, and S5) remains unchanged during the recovery process in thisembodiment.

FIG. 4A is a flow diagram of a process 400 illustrating an embodiment ofthe present invention. The process 400 begins (405) and configuresmultiple nodes and links to distribute media (e.g., video) in a ringnetwork. Configuring the multiple nodes may be done by a serviceprovider in a manual manner or using a Network Management System (NMS).Other typical ways of configuring multiple nodes and links to distributemedia in a ring network may also be employed. MPLS VPLS techniques maybe used to configure the nodes and links. After configuring the multiplenodes and links, the process 400 may disable distribution of the mediaon a communications link between a selected pair of adjacent nodes inthe ring network in a manner maintaining communications between theselected pair of adjacent nodes other than for distribution of the media(415). By disabling distribution of the media on a communications link,the ring network is changed to be a “horseshoe” topology with respect todistribution of the media. The process 400 ends (420) thereafter and isset to adapt to a communications link failure or node failure in amanner as described above in reference to FIGS. 1A-1C, 2A-2F, and 3A-3D.

FIG. 4B is a flow diagram of a process 401 that includes the configuring(410) and disabling (415), as described above in reference to FIG. 4A,and also includes distributing the media (425) during an operationalstate of the network. Thus, FIG. 4A may relate to an example in which amanufacturer or distributor configures the network to operate accordingto an embodiment of the present invention, and the example embodiment ofFIG. 4B may relate to a service provider (or other party) in which theservice provider configures a network and distributes the media on thenetwork, optionally with contribution from a media content provider,such as a video distributor.

FIG. 4C is a flow diagram of a process 402 that may be used in thenetwork embodiments of FIGS. 1A-1C or FIGS. 3A-3D. The process 402begins (430) and adds media to a head-end ingress node on a ringtopology (435) receiving media from a head-end node, as described inreference to FIGS. 1A-1C and 3A-3D. A determination may be made as towhether the head-end ingress node is a single node or a pair of nodes(440). The process 402 continues in two different, but similar, pathsdepending on whether the head-end ingress node is a single node or apair of nodes, as described above in reference to FIGS. 1A-1C or FIGS.3A-3D.

If the ingress node is a single node, the process 402 determines whetherthe ingress node is one of the nodes in the pair of selected adjacentnodes between which the communications link is disabled (445). If theingress node is one of the nodes in the selected pair of adjacent nodes,the media is distributed in one direction on the ring topology (450). Ifthe ingress node is not one of the nodes in the selected pair ofadjacent nodes (445), the media is distributed in two directions on thering topology (455). Either way, the process 405 continually orcontinuously determines whether there is a link or node failure (460).If there is no failure (460), the process 402 continues to distributethe media downstream in one or two directions (450, 455) on the ringtopology. If there is a link or node failure, the communications linkbetween the selected pair of adjacent nodes is enabled to distribute themedia (465). After the communications link is enabled, the media isdistributed via the communications link between the selected pair ofadjacent nodes until the failure is corrected (470). In someembodiments, a PSW riding on an LSP, which traverses the enabledcommunications link and other communications links, is employed todistribute the media.

In an event the failure is corrected, it should be understood that thecommunications link between the selected pair of adjacent nodes mayagain be disabled to re-establish the “horseshoe” configuration asdescribed above in reference to FIGS. 1A and 3A.

If the head-end ingress node connected to a head-end node is a pair ofnodes (440), distribution of the media on a communications link betweenthe pair of ingress nodes is disabled (475). Media is thereafterdistributed (480), and continual or continuous checking as to whetherthere is a link or node failure (485) ensues. If there is no failure,distribution of the media (480) continues. If there is a link or nodefailure, then, if the failure node is a node in the pair of head-endingress nodes, the distribution of the media on the communications linkbetween the selected pair of adjacent nodes is enabled until the failedingress node is fixed (i.e., in a working state) (495). If there is alink failure or a node failure that is not one of the pair of ingressnodes (485), distribution of the media on the communications linkbetween the ingress nodes and the selected pair of adjacent nodes isenabled until the link or node is fixed (490). Thereafter, distributionof the media (480) continues in the failure recovery configuration untilthe failed node or communications link is fixed. Once the node orcommunications link is fixed, the network configuration can return tothe initial state of a “horseshoe” configuration.

FIG. 5A is a network diagram illustrating an aspect of an exampleembodiment of the invention. The network diagram includes a network 500,which includes a ring network 505 with multiple nodes 510 interconnectedvia communications links 515. In the ring network 505, there are primaryLSPs 520 traversing the communications links 515 and primary VPLSconnections 525 riding on the primary LSPs 520. A logical break 535 a isinitially configured between a selected pair of adjacent nodes 530 a,530 b, thus creating the “horseshoe” topology in the ring network.

In an event of a link failure (e.g., link cut) 570, an exemplaryembodiment of the invention engages a primary backup LSP 572 and primarybackup VPLS connection 571 to carry media or network communicationsbetween nodes F and E. To do so, the initially configured logical break535 a is enabled, and a logical break 535 b is “logically moved” to thecommunications link 515 where the physical link failure 570 occurs. Itshould be understood that computer memory, such as a data table ormemory register, may change states or not change states, depending onthe implementation, to reorganize the “horseshoe” topology from (i)having a disabled communications link 515 between the selected pair ofadjacent nodes 530 a, 530 b to (ii) having a disabled communicationslink 515 where the link failure 570 occurs, such as between adjacentnodes E and F. After the link failure 570 is repaired, the logical break535 a can be configured again between the selected pair of adjacentnodes 530 a, 530 b.

FIG. 5B is a network diagram of the network 500 illustrating anotheraspect of the example embodiment of the invention. In an event of a nodefailure 575, the example embodiment of the invention may enable theinitially configured logical break 535 a and logically assert a logicalbreak 535 b upstream or downstream of the node failure 575.

In this example embodiment, a secondary backup LSP 574 a (logical), 574b (physical) may be employed to allow communications transporting media565 to flow to node D, which includes flowing the media 565 across theinitially disabled communications link 515 between the selected pair ofadjacent nodes 530 a, 530 b. A backup VPLS connection 573 a (logical),573 b (physical) rides on the secondary backup LSP 574 a, 574 b,respectively. The secondary backup LSP 574 a (logical) may be referredto as a “skip one” secondary backup LSP 574 a (logical) because it“skips” (logically) over the node failure 575 in the downstreamdirection. If two nodes downstream of a head-end ingress node, node A,fail, the example embodiment may use a “skip two” secondary backup LSP(not shown) in the downstream direction. Because communications cannotactually pass through the failed node 575, the “skip one” secondarybackup LSP 574 b (physical) traverses the physical links 515 of the ringnetwork 505, via the nodes 510 from node F to node D, including acrossthe re-enabled communications link 515 between the selected pair ofadjacent nodes 530 a, 530 b.

As illustrated in FIGS. 5A and 5B, distribution of media 565 can beinitially disabled on a communications link 515 to form a “horseshoe”topology in a ring network 505. Primary communications paths 520 totraverse the communications links 515, other than between the selectedpair of adjacent nodes 530 a, 530 b, can be configured, and primaryconnections 525 to distribute the media 565 to each of the nodes 510 onthe communications paths 520, including to the selected pair of adjacentnodes 530 a, 530 b, can also be configured. First backup communicationspaths 572 and 571 that use the primary connections 525 between adjacentnodes 510, other than between the selected pair of adjacent nodes 530 a,530 b, can be configured. Second backup communications paths 574 a(logical), 574 b (physical) and secondary connections 573 a (logical),573 b (physical) between non-adjacent nodes (e.g., nodes F and D) canalso be configured. In an example embodiment, the first backupcommunications paths 572 and 571 may be activated in an event of a linkfailure 570, and the second backup communications paths 574 a (logical),574 b (physical), 573 a (logical), 573 b (physical) may be activated inan event of a node failure 575.

Any number of second backup communications paths 574 a, 574 b can beconfigured in a manner as described above in reference to FIGS. 5A and5B, or as otherwise understood in the art, to support communicationsfailures on communications links or nodes. A Virtual Private Local AreaNetwork (LAN) Service (VPLS) connection may be used, or another form ofmulti-protocol label switching (MPLS) technique, may be used inaccordance with example embodiments of the invention. Label SwitchedPaths (LSPs) may be configured as the communications paths 520, 574 b,or other form of paths carrying communications supporting media 565 maybe employed.

FIG. 6 is a flow diagram 600 illustrating aspects of an exampleembodiment of the invention. The flow diagram begins (605) andconfigures a “horseshoe” network topology from a point of view of atleast some media (610). The “horseshoe” network topology is configuredfrom a ring network by disabling a communications link between aselected pair of adjacent nodes. Primary communications paths andconnections are configured (615). First backup communications paths,which use the primary connections, are configured between adjacent nodes(620). The second backup communications paths and secondary connectionsare configured between non-adjacent nodes (625). The flow diagram 600ends (630), allowing typical network communications to occur withfailover conditions facilitated by the first and second backupcommunications paths.

FIG. 7 is a block diagram 700 illustrating an example embodiment of theinvention in which a monitoring unit 710 and activation unit 715 may beemployed during operation of a network. The monitoring unit 710 mayreceive a communications link failure input 705 a and a node failureinput 705 b. It should be understood that the inputs 705 a, 705 b may bereceived on separate ports at the monitoring unit 710 or in a singleport (not shown) in the monitoring unit 710.

The input 705 a, 705 b may be in the form of communications, errorsignals, or other typical network signals used for such a purpose.Moreover, the communications link failure input 705 a or node failureinput 705 b may also be in the form of an absence of signals to themonitoring unit 710. Regardless, the monitoring unit 710, in an event ofa failure, may send failure information 715 to the activation unit 720.In turn, the activation unit 720 may process the failure information 715and determine whether to send activation data 725 a or 725 b to activatebackup communications paths that use primary connections betweenadjacent nodes 730 a or activate backup communications paths that usesecondary connections between adjacent nodes (e.g., every second node,third node, and so forth) (730 b).

It should be understood that the activation unit 720 may activate thebackup communications paths independently, via signaling through a MPLSsignaling protocol, provisioning channel, or other technique to activatethe backup communications path(s). Moreover, the activation unit 720 mayalso be employed to re-enable the disabled link between the selectedpair of adjacent nodes (e.g., nodes C and D 530 b, 530 a, respectively,in FIG. 5B) in accordance with the example embodiments described inreference to FIGS. 5A and 5B, or other figures described herein.

The monitoring unit 710 and activation unit 720 may be implemented inhardware, firmware, or software and may be employed in each node of aring network, at a central data collection node of a ring network, orother node associated with a ring network. If implemented in software,the monitoring unit 710 and/or activation unit 720 may be stored on anyform of computer-readable media in the form of processor instructions.The processor instructions can be loaded and executed by any form ofcustom or general processor adapted to operate in networkconfiguration(s) as described herein. In one example embodiment, themonitoring unit 710 and activation unit 720 may be available in softwarethat can be downloaded to some or all of the nodes of a ring network.

FIG. 8 is an example table 800 stored in one or more nodes in a ringnetwork, or associated with a ring network, that may be used to signal,provision, or provide instructions for manually configuring backupcommunications paths in an event of a communications link failure or anode failure in a link network.

First backup communications paths, which use primary connections betweenadjacent nodes, are indicated in the top row 805 of the table 800. Asillustrated, node A has a first backup communications path to node B,node B has a first backup communications path to node C, node C has afirst backup communications path to node D, . . . , and node n has afirst backup communications path to node A, which completes the firstbackup communications path around the ring network. It should beunderstood that backup communications paths may also be found traversingthe communications links of the ring network in the opposite direction(not shown for brevity).

The table 800 may also include an illustration of second backupcommunications paths, which use secondary connections betweennon-adjacent nodes, in the second row 810, third row, 815, fourth row820, and so forth. As illustrated, one of the second backupcommunications paths (row 810) has a “skip one” methodology, the nextlower row (row 815) of second backup communications paths has a “skiptwo” methodology, the next lower row (row 820) of second backupcommunications paths has a “skip three” methodology, and so forth.

The second backup communications paths can be preconfigured hierarchiesof paths or hierarchies of paths that are determined during operation.The multiple levels of hierarchy (i.e., rows 805, 810, 815, and 820, andso forth) may be employed as needed in an increasing order as failuresin a network occur. For example, if a communications link failureoccurs, the first backup communications paths (row 805) may beactivated. If a network node failure occurs, a “skip one” second backupcommunications path (row 810) may be activated. If two adjacent nodesfail, a “skip two” second backup communications path (row 815)methodology may be activated, and so forth.

While this invention has been particularly shown and described withreferences to example embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

1. A method of distributing media on a ring topology communications network, comprising: configuring multiple nodes and communications links to distribute media in a ring network; and disabling distribution of the media on a communications link between a selected pair of adjacent nodes in the ring network in a manner maintaining communications between the selected pair of adjacent nodes other than for distribution of the media.
 2. The method according to claim 1 further comprising distributing the media to the multiple nodes including the selected pair of adjacent nodes.
 3. The method according to claim 1 wherein disabling distribution of the media between the selected pair of adjacent nodes includes disabling distribution of the media on a communications link between adjacent head-end ingress nodes that receive the media downstream from a head-end node that receives the media from a node external from the ring network.
 4. The method according to claim 1 further comprising: adding the media to a head-end ingress node on the ring network; and distributing the media from the head-end ingress node in two downstream directions around the ring network other than on the communications link between the selected pair of adjacent nodes.
 5. The method according to claim 1 wherein, in an event of a failure (i) in a communications link other than between the selected pair of adjacent nodes or (ii) of a node other than one of the selected adjacent nodes, enabling the communications link between the selected pair of adjacent nodes to distribute the media.
 6. The method according to claim 1 further comprising: configuring a pair of head-end ingress nodes on the ring network to receive media on separate communications paths from a node external from the ring network; disabling distribution of the media on a communications link between the head-end ingress nodes; and configuring the pair of head-end ingress nodes on the ring network to distribute the media on the ring network in respective downstream directions.
 7. The method according to claim 6 further including in an event of a failure (i) of a communications link other than a communications link between the head-end ingress nodes or the selected pair of adjacent nodes in the ring network or (ii) a node other than a head-end ingress node in the ring network, enabling distribution of media on the communications link between the pair of head-end ingress nodes and the communications link between the selected pair of adjacent nodes.
 8. The method according to claim 6 further including, in an event a head-end ingress node in the pair of head-end ingress nodes fails, enabling distribution of the media on the communications link between the selected pair of adjacent nodes.
 9. The method according to claim 1 wherein configuring the multiple nodes and communications links includes employing a Virtual Private LAN Services (VPLS) to distribute the media.
 10. The method according to claim 1 further comprising: configuring at least a subset of the nodes to drop the media locally; or running a protocol associated with respective nodes that determines if the media is to be dropped locally by the respective nodes.
 11. The method according to claim 1 wherein configuring the multiple nodes includes signaling or provisioning Label Switched Paths (LSPs) between adjacent nodes.
 12. The method according to claim 1 wherein configuring the multiple nodes and communications links includes configuring Layer 2 communications on the ring network.
 13. The method according to claim 1 wherein disabling distribution of the media on the communications link between the selected pair of adjacent nodes defines a static logical break in the ring topology.
 14. The method according to claim 1 wherein the media includes video content.
 15. A network, comprising: multiple nodes and communications links configured to distribute media in a ring network; and a communications link between a selected pair of adjacent nodes in the ring network disabled in a manner maintaining communications between the selected pair of adjacent nodes other than to distribute the media.
 16. The network according to claim 15 wherein the multiple nodes distribute the media, including to the selected pair of adjacent nodes.
 17. The network according to claim 15 wherein the selected pair of adjacent nodes receive the media downstream from a head-end ingress node on the ring topology that receives the media from a node external from the ring topology.
 18. The network according to claim 15 further comprising a head-end ingress node configured to add the media on the ring network and distribute the media in two downstream directions around the ring network other than on the communications link between the selected pair of adjacent nodes.
 19. The network according to claim 15 wherein, in an event of a failure (i) in a communications link other than between the selected pair of adjacent nodes or (ii) of a node other than one of the selected adjacent nodes, the communications link between the selected pair of adjacent nodes is, enabled to distribute the media.
 20. The network according to claim 15 further comprising: a pair of head-end ingress nodes on the ring network coupled to a node external from the ring topology via separate communications paths that add the media to the ring network in respective downstream directions from the pair of head-end ingress nodes; and a communications link between the pair of head-end ingress nodes disabled from distributing the media.
 21. The network according to claim 20 wherein, in an event of a failure (i) of a communications link other than a communications link between the head-end ingress nodes or the selected pair of adjacent nodes in the ring network or (ii) a node other than a head-end ingress node in the ring network, the communications link between the pair of head-end ingress nodes and the link between the selected pair of adjacent nodes are enabled to distribute the media.
 22. The network according to claim 20 wherein, in an event one of the nodes of the pair of head-end ingress nodes fails, the communications link between the selected pair of adjacent nodes is enabled to distribute the media.
 23. The network according to claim 15 wherein the multiple nodes and communications links are configured using Virtual Private LAN Services (VPLS) to distribute the media.
 24. The network according to claim 15 wherein: at least a subset of the nodes are configured to drop the media locally; or further comprising: a protocol associated with respective nodes that determines that the media is to be dropped locally by the respective nodes.
 25. The network according to claim 15 wherein the multiple nodes are provisioned using Label Switched Paths (LSPs) between adjacent nodes.
 26. The network according to claim 15 wherein the multiple nodes and communications links are configured using Layer 2 communications on the ring network.
 27. The network according to claim 15 wherein the communications link disabled between the selected pair of adjacent nodes defines a static logical break in the ring network.
 28. The network according to claim 15 wherein the media includes video content. 